The Demon
by Awkward iguana
Summary: A powerful force returns to Ooo from the Nightosphere,and threatens to destroy all life.(Contains Finnceline)
1. Chapter 1

**Hey fanfiction! I'm new here, and I figured I might as well start right away with an Adventure Time fanfic. So leave two characters in the reviews or, PM me and I'll make a fanfic about em:D Edit:okay since no one cares enough to leave two characters I'm just gonna make this finnceline.**


	2. Chapter 2

**Hello** **Readers! I apologize for taking so long to update the story. Now please remember, this is my first fanfic so it might not be great. I will accept any help, now without further ado, I give you my fanfic!(Finn is 18 here, and flame princess doesn't exist.)**

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It was a normal day in the land of Ooo.(As normal as Ooo can get.)The Candy Kingdom was bustling,as well as every other Kingdom. The birds were chirping,the bee's were buzzing,and Finn and Jake were out adventuring."Jake look out!",Finn exclaimed just in time, as the tentacle monster they were fighting took a swipe at Jake's head. Jake dodged the tentacle and delivered a blow to the monster's face."Thanks man." Jake said.

"No pro-",but before Finn could finish his sentence,he was swiped to the side by one of the beast's tentacles,and slammed into a tree. He stumbled to his feet and picked up his sword."That's gonna hurt in the morning." The beast then did the same move but with 2 tentacles. Finn rolled out of the way,and cut of the monster's tentacles. The monster was stunned so Finn moved in for the kill. He cut off it's head and the monster fell over,dead. Finn sighed in relief that the battle was over,as did Jake.

As they walked home Finn was thinking of what to do next."Hey Jake,wanna go to Marceline's place?"

"Well I thought we could just go home,cause I'm kinda tired.",Jake replied.

"Come on it's to early to go home,and she might have some cool song she needs help on."

"Why are you so intent on going to Marcy's place?"

"N-No reason",he said awkwardly.

"Fine let's go"

"_Whew that was a close one"_,Finn thought to himself.

Of course there was a reason,and Finn knew precisely what it was. He. Had a crush. On Marceline The Vampire Queen. He didn't know when it had started,but he knew he was definitely in love with Marceline. They arrived at Marceline's house and let themselves in._"Where is she?"_,Finn thought."I'm gonna go find Marcy." Jake replied with a nod. Finn looked upstairs,and saw the bathroom door was open. Being curious he walked in and saw a familiar sight. Marceline,fully naked preparing herself a bath. Her breasts were huge,and she had curves in all the right places. Sure,Finn had seen her naked before,that one time when he was hiding in her closet,but he didn't pay attention then.

She turned around,and screamed,"FINN WHAT ARE YOU DOING HERE!"Finn covered his eyes."Sorry I didn't know!" He stumbled back,tripped over a lamp on the floor,and hit his head off a dresser."OW OW OW!"

"Finn are you ok?!",Marceline said,now with a towel on.

"Yeah I'm fine", he said in pain.

"Why were you watching me!?"

"No I wasn't it was an accident I swear."

Jake heard the noise,and came upstairs."What's going on!",Jake exclaimed.

"Finn was watching me naked!"

"No I wasn't!" After much arguing they had concluded Finn didn't mean to see her.(Not saying he didn't enjoy it.)Finn and Jake left Marceline's house to return to their own._"Finn saw me naked,I wonder if he liked it. Wait what am I saying?! Why would I even think like that!? Wait,I did feel a little excited when I saw him. I wonder if...No. I can't be having feelings for him,can I? That would explain all the times I've been more happy than usual to see him." Marceline continued to think through the day._

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**I apologize again for taking so long. This chapter didn't really help the plot. I will take help.**


	3. Chapter 3

**Hello readers! Enjoy the new chapter!**

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The next day Marceline still hadn't narrowed down if she had feelings for Finn or not._"I can't have feelings for him,he's just a mortal"_,she thought to herself. Meanwhile Finn was bored and trying to decide what to do._"Maybe I'll ask Jake what he wants to do._ Ja-_Oh damn he's sleeping. Oh well,I'll just go find something to do on my own."_ Finn walked outside and looked around for something to do, when he saw The Candy Kingdom._"I guess I could go see what PB is up to." _ Finn arrived at The Candy Kingdom,and the gates were immediately opened. Since Finn was a hero he was allowed virtually anywhere. He let himself into The Candy Castle,and went to Princess Bubblegum's lab. If this were his first time here,he would be completely lost,but since he had been here more times than he could count,he knew the place inside and out.

He let himself into her lab,and saw her making some kind of potion."Hey PB,what's up?"

"Oh Finn! I was just going to go looking for you."

"Why?"

"I wanted you to test out this new potion I made."

"Ok then give it here."

"Here you go." Finn took the potion,and drank it."Bleh! It tastes horrible!"

"Sorry,I haven't perfected the formula yet."

"What is this?"

"Hair growth formula." Finn's hair grew down to his feet,and became more bushy."I haven't had my hair this,long since before I gave it to that tree witch." Princess Bubblegum then helped Finn cut his hair. "Got anything else for me to test out?"

"Sadly no."

"Oh well. I guess I'll just go then."

"See ya later Finn."

"Se ya._ Well that didn't really help kill any time. Guess I'll just-"_ His thoughts were interrupted by Marceline floting in the distance._"Hey it's Marcy!" _He began to walk towards her,but stopped as he remembered the events of yesterday._"Maybe I should wait a day to talk to her again." _Meanwhile in Marceline's thoughts._"No,there's no way I'm in love with him,no way I'm in love with him! He's just a mortal and I'm...immortal. Hey,is that Finn? Maybe I should...no I shouldn't talk to him until I've figured this out."  
_

Finn and Marceline managed to avoid each other,and Finn returned home."Hey man where were you?",Jake said as his brother walked through the door.

"I was helping PB with one of her experiments."

"Cool,want some bacon pancakes?"

"Isn't it a little late in the day for bacon pancakes?"

"It's never too late for bacon pancakes,man."

"Whatever man." Finn walked to his room and sat on the edge of the bed,when he felt a sharp pain in his chest."Ah! W-what the hell?!" He fell on the ground,writhing in pain. He clenched his chest."What the hell is h-hapening to me?!" He then passed out on the floor.

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"Finn? Hey Finn wake up!"

"Ugh what happened?"

"I came up here,and found you on the floor,so I put you on the bed."

"How long ago was this?"

"About an hour ago."

"An hour?!"

"Yeah you were out for a while. Marcy came by,but I told her to come back later."

"What,why?! You could've said wait."

"I didn't know when you'd wakd up. Why are you making a big deal of this?"

_"Oh crap_._"_,he thought."Well what if it was important?"

"I think she would've waited."

"Oh then there was no reason to be worried ha ha",Finn said extremely awkwardly.

"Rrriiiiight.",Jake said in a,'I am going to ignore what you just said',tone.

_"There's no way he bought that"_,Finn thought.

"Anyway,back to the subject of you passing out on the floor. How did that happen?"

"I'm not sure. All I remember was,feeling a pain in my chest,and then you woke me up."

"Huh weird."

"You're tellin me. That's never happened to me before."

"Hmm maybe you have some disease.",Jake said worried.

"I doubt it."

"Still it won't hurt to check."

"Fine,let's go check a hospital." They arrived at The Candy Hospital(since it was the only hospital the knew),and they got a scan. "I could not find anything wrong with you Finn.",stated the doctor.

"Weird. Thanks anyway doc."

"No problem Finn." They then returned to their Tree Fort."Well that was weird",said Finn.

"Yeah I guess we just go on as normal." Before they could sit down and relax,there was a answered the door to find Marceline floating there."H-hey Marcy"

"Hey Finn I was wondering if-"

_"Maybe she'll ask me out!" _Marcy finished her sentence."-you wanted to have a jam session?"

_"Oh._ Sure Marcy",he said slightly disappointed. After the jam session Finn returned home,and went to sleep. Finn tossed and turned in his sleep,constantly hearing voices. He was suddenly in a strange dream where a figure stood before him."Where am I? Who are you?"

"That's none of your business. You shouldn't even see me right now you're mentally stronger than I thought."

"Who are you,and what are you talking about!?"

"Like I said that's none of your business." Finn woke up drenched in sweat."What the hell was that about?" Finn walked to the bathroom,and splashed some water on his face. He looked in the mirror,and screamed,nearly waking up Jake. He saw a morphed version of himself. Sharp teeth,blood red eyes,and demon skin. Finn rubbed his eyes,and was relieved to see his reflection was normal."What the hell is going on?!"

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**Sorry for the cliff hanger. I also apologize for taking so long to update,I'm busy. The Bubblegum part didn't serve a purpose accept to introduce her. I'll try to update sooner.**


	4. Chapter 4

**Hello readers! As some of you noticed I changed the title and summary. I also apologize for taking so long to update(I have school).**

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Finn was in a state of panic. He had no idea what was going on,and believed he was going insane."What the fuck is going on?!",he said panicked."I just need to calm down I'm probably just dreaming."

"Believe me,this is no dream."

"Who said that?!"

"Look in the mirror." Finn did as he was told,and looked in the mirror. He saw the same warped version of himself. The demon spoke to him."Look into my eyes." Finn knew it was probably a bad idea,but he couldn't help but look into his eyes."Good now hold still." There was a flash,and Finn woke up in his bed."What the hell was that?" Finn got dressed,and went downstairs."Hey sleeping beauty.",said Jake."What's up?"

"I had a weird dream."

"What was it about?"

"Well it was really complicated. First there was this figure,and then when I went to the mirror there was this...this thing that looked like me but it didn't."

"You're not making any sense whatsoever."

"Yeah I know,but it felt so real."

"Weird."

"You're tellin me. Oh,and there was this demon too."

"Maybe we should get some help."

"Well who's gonna help?"

"You said there was a demon right?"

"Yeah so?"

"So,who do we know that's an expert on demons?"

"Marcy!" They arrived at Marceline's house,and explained the situation to her."And you came to me,why?",said Marceline.

"Well we thought,since it envolved demons,we thought you could help."

"It sounds like you just had a bad dream. It could have something to do with demons,but I doubt it. If the same thing happens again,I guess you could come back,but I doubt I'll be able to help."

"Oh well. Thanks anyway Marcy."

"Don't worry about it. Oh and Finn."

"Yeah?"

"I uh w-well I...never mind."

"Ok then." Finn and Jake then left for their own house._"Damn. Why didn't I tell him?"_,thought Marceline to herself.

_"I wonder what Marcy wanted to tell me,and what was that dream about? Maybe I should clear my mind."_,thought Finn._  
_

"Hey Jake I'm gonna go out for awhile."

"Alright see ya later."

Finn walked off,and was thinking of something to do,when a gang member jumped out of alleyway with a knife and attempted to stab Finn. Finn dodged the knife,grabbed the thug's arm,flipped him over,and calmly said,"May I help you?" The thug grabbed his knife and scrambled to his feet. "You're that goodie twoshoes,ain't ya?!"

"That would be me."

"You put half my crew in jail! Now you're gonna pay for it!"

"Ah this again. Well let's get started,give me your best shot." The thug ran at him,but Finn dodged it."Oh,so close!",said Finn.

"Hold still!",exclaimed the crook.

"That still wouldn't give you any advantage."

"Shut up!"

"Just sayin." The thug tried again,but of course failed."My turn." Finn began pounding the crook,and found it even easier than usual. He started to get carried away,and continued pummeling him long after he was beaten."Please stop,I give I give!",cried the crook.

"This what you get asshole!",he said between punches."Now,you're gonna tell you're crew not to mess with me. Got it?!"

"Please let me go!",the crook said bloody and beaten.

"I said,got it!?"

"Yes,yes! Now please let me go!" Finn threw the crook to the side and walked away.

_"Stupid ass_ _thug."_,Finn thought to himself. Finn continued to look for something to do. He saw Marceline's house and a devious thought popped into his head. He walked towards Marceline's house. He made it there,and knocked on the door."Oh hi Finn.",Marceline said.

"Hey Marcy.",Finn walked in and sat on the couch.

"What's up Finn?"

"Just came to see you." Marceline blushed. Finn patted the seat next to him,and Marceline sat/hovered next to him. "So what's been goin on",asked Finn.

"Oh just thinking."

"About what."

"Oh you know...stuff."

"Whatever.",Finn said. After some time Finn smelled something,leaned over to Marceline,and sniffed her. Marceline blushed at the sudden action."Mmm,strawberries.",Finn said.

"F-Finn?"

"Yeah?"

"What're you doing?"

"Just noticed you smelled like strawberries."

"Y-yeah I had some earlier."

"Well it's nice."

"T-thanks."

"Yeah...Ya know,you're eyes are really beautiful."

"T-th-thanks." Marceline was blushing madly at the strange actions Finn was portraying. She noticed how close they were,and blushed even harder."F-Finn I..."

"Shhh" Finn began to lean in...**KNOCK KNOCK._  
_**_"Dammit",_Finn thought. He got up and answered the door,to see Princess Bubblegum."Finn!"

"Hey PB."

"Finn I need to talk to you...in private."

"Okay see ya Marcy."

"S-see ya.",she said still confused at what happened between her and Finn._"I can't believe that.",_she thought,humiliated that a mortal made her feel that way.

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**Did Finn seem OCC? Good,that's part of the plot;)**


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